Other less hazardous dangers may be hidden in the trailside foliage. Poison oak (Toxicodendron diversilobum) is thick along the trail and elsewhere, so avoid brushing up against either its foliage or bare branches. In addition, deer ticks are present. Deer ticks (Ixodes pacificus) are potential carriers of Lyme disease. The best way to avoid both poison oak and deer ticks is to wear long pants. For more info. on hazards see: http://nrs.ucdavis.edu/stebbins/technical/hiking.htm

A Natural History Hike for All SeasonsThis tour describes sights along Cold Canyon’s Homestead Trail.

1. Outlet of Cold Creek (unmarked). Start at the parking area 0.2 miles past the bridge over Putah Creek on the right-hand side. In this area you can view the lowermost reaches of Cold Creek, which flows out of Stebbins Cold Canyon Reserve. The channelization here was completed in 1995 to enable water to move quickly through the area after floods created huge debris flows. Just upstream of the mouth of Cold Creek is a major spawning area for wild trout in Putah Creek. If you return to this spot in December or January, you may be able to see the shadowy forms of large trout spawning in the riffles.2. Roadcut (unmarked). As you walk up the road to the trail, observe the exposure of bedrock on the slope to your left. This exposure consists of many layers of sandstone and is part of the Sites Formation, the bedrock forming the entire eastern slope of Cold Canyon.3. Main Gate. Just inside the gate, the trail forks. The left fork is the Pleasants Ridge trail, which winds up the hill through savanna dominated by blue oaks (Quercus douglasii), to the top of the eastern ridge. The right fork marks the start of the homestead trail.4. Poison oak. If you are not familiar with poison oak, use these plants as a standard. 5. Redbud (Cercis occidentalis) starts the season with a gorgeous display of magenta blossoms, followed by its heart-shaped leaves. It often sheds these in the heat of the summer, so that by fall, its brown bean-shaped fruits may be all that remain on the branches.

Hiking in Stebbins Cold Canyon Reserve

Stebbins Cold Canyon Reserve is one of the few natural reserves in the University of California Natural Reserve System that serves the dual purposes of academic research and public use. The 636 acres of the reserve are nestled in the Vaca Mountains, the eastern-most ridge of the North Coast Ranges. More information on the reserve’s natural history is available at its website (http://nrs.ucdavis.edu/stebbins.html).

Guided outings on a variety of nature subjects in the arts and sciences are available to the public free of charge. These presentations and hikes take place in the spring, early summer and late fall. If you are interested in obtaining a current schedule, becoming part of the PRESERVE THE RESERVE community that maintains the reserve or if you would like to become a guide, contact jfalyn@ucdavis.edu.

Reserve RulesStebbins Cold Canyon Reserve is open for hiking year-round, every day, from sunrise to sunset. To keep the reserve as beautiful and as wild as you find it, please follow some simple rules when you hike in Cold Canyon.1) Please sign the register located at the reserve entrance.2) Do not collect plants, animals, or other organisms.3) Do not disturb research sites or management areas (indicated by colored tape, flags, or signs), and obey any signs restricting access to trails.4) Minimize signs of your presence. Please pack out anything you bring in, especially trash. If you see trash left by other people, pack that out as well.5) Bikes, dogs, fires, and guns are not allowed on the reserve.The Trail Sytem in Cold CanyonThere are three main hiking trails in Cold Canyon, as shown on the trail map. The Homestead Trail starts at the main gate by the road and runs up the canyon to the old Vlahos homestead and Cold Storage Area. This one mile one-way trail is easy to moderate. The Blue Ridge Loop Trail begins 100 yards west of the main gate, on the west side of the creek. This trail takes you up to the western peaks overlooking Cold Canyon and Lake Berryessa. Views are spectacular. The trail is steep, but switchbacks installed in 2007 make it managable. It proceeds along the ridge and loops back to the old stone Homestead foundation. The full loop is a challenging 5 miles. The

Pleasants Ridge Trail begins at the left fork just inside the main gate. This very steep and unmaintained trail runs up to the top of the eastern ridge. Use caution when climbing this one mile trail.Potential Hazards of Cold CanyonCold Canyon is a beautiful area, but it has its hazards. The trail has become quite rough and steep in places as a result of landslides, and creek crossings contain slippery rocks. Watch your step! In the summer, and even in the spring, Cold Canyon can get quite warm, so the best time to hike is during the cooler morning. If you plan to hike later in the day, bring a hat and water to prevent heat exhaustion during hiking. Three species of vertebrates living on the reserve are potentially dangerous. Mountain lions, black bears, and rattlesnakes are present, although your probability of encountering these species is remote. Mountain lions can be more dangerous than bears and snakes, always travel with a partner, and keep children in sight. In the very rare case that you encounter a moutain lion, act threatening: stand your ground, make noise, stand tall, and if necessary, throw sticks or rocks.

6. Landslide. At the first bend are the remains of a major landslide that resulted from the heavy rains of 1995. The debris flowed out of the dry canyon (on your left as you face upstream). The debris flow eliminated much of the riparian vegetation in the creek below and nearly took out the highway as well.7. Fork to Blue Ridge Trail. Just after you cross the slide, you will see a large rock on your left that is covered with small circular patches of greenish and rust-colored lichens. Lichens (a fungi-algae symbiotic organism) gradually dissolve rocks, and therefore contribute to the weathering of rock into soil. The trail to the right marks the start of the Blue Ridge Trail.8. Interior live oak. Proceed along the trail across a boulder-strewn area, more remains of the 1995 landslide. In the spring and summer, you can often see western fence lizards (Sceloporus occidentalis), basking on rocks. In the midst of this area is a large interior live oak (Quercus wizlizenii) that managed to survive the slide.9. Coyote brush (Baccharis pilularis) can be found in many spots along the trail. This species is notable because it is dioecious: each individual plant is either male or female, just like in humans. In contrast, most other plants produce both seeds and pollen on the same plant - usually within a single flower.10. Sign-in area. This marks the official entrance to the reserve. Please sign in. Just past the sign-in box, a toyon (Heteromeles arbutifolia) grows on the right side of the trail. If you visit in the fall or winter, its bright red fruit will be visible.11. Slide area. About 100 m up the trail is a flat open space that resulted from another slide. Next to the trail at this point, there is skunkbrush (Rhus trilobata). It is a close relative of poison oak and can easily be confused with it. It does not cause skin irritation.12. Manzanita. The shrubs with pastel-green leaves and reddish, twisted branches are parry manzanita (Arctostaphylos manzanita). This plant is common in chapparal, along with chamise (Adenostroma fasciculum) and toyon.13. Yerba santa. In the summer, yerba santa (Eriodictyon californicum) is almost more formidable looking than poison-oak; its long dark oily leaves make it appear particularly noxious. While this oil may in fact ward off potential herbivores, it has several medicinal properties for humans.

The trail system in Cold Canyon. Numbers along the Home-stead Trail indicate the locations of the hiking tour markers. A topographical map is available on the website.

Poison oak

Deer Tick

Yerba santa

14. Bay trees. Large bay trees (Umbellularia californica) stand on your right. These have relatively thin, straight limbs and light gray bark. Their leaves are narrow and smooth-edged, and give off a pleasant, pungent smell when rubbed.15. Rocky peak on right. As the trail starts to climb, marked by wooden erosion control bars, note the rocky peak across to the right. Usually, you can see raptors soaring around it. In the moist areas along the left side of this section of trail, milkmaids (Cardamine californica), a delicate white four-petaled flowers, begin blooming starting in February. Look also for ferns and bushes of the sticky monkeyflower (Mimulus aurantiacus). The bright orange-yellow tubular flowers that bloom in the spring make this one of the showiest chaparral shrubs.16. Old landslide with buckeyes and more. When the trail starts to climb abruptly with some “stairs,” you will know you are crossing a landslide that occurred in 1982. Actually, it was more of a land slump because a good chunk of the hillside slid downwards with much of the vegetation still on top. In very early spring, shooting stars (Dodecatheon hendersonii) blooms along the bank here. Numerous California buckeyes (Aesculus calfornica) grow along this section of the trail. They can be identified by their smooth, pale gray bark. In spring, their large compound leaves make this area very lush. In the late spring, their showy flowers bloom-look for large candelabras of small white or pink flowers. Both flowers and leaves wither over the summer, revealing the developing fruits. Just south of the sign, a large California pipevine (Aristolochia californica) is climbing up a buckeye. Look for flowers in mid-February.17. Intermittent drainage. Just before this drainage in front of you is an open area that will allow you to see the steep slope on the opposite side of the creek. A flow from a small landslide scars this slope. You can follow the scar up to a small landslide “scarp,” the ragged wall of soil exposed by the earth that tumbled down the slope. Thousands of years ago, a much larger landslide occurred: the sheer cliff forming the peak above you is the remains of the much older landslide scarp. The earth that was

moved in this landslide now forms the entire hill slope below the cliff, extending both to the left and right of the cliff in a relatively flat line along the hill. As you cross the drainage, look for several plants of the foothill lupine (Lupinus albifrons), a round shrub with silvery-gray leaves and spikes of blue flowers that bloom mid-spring.18. Wild grapes. Soon you will step out of the wooded area into a section of the trail bordered on either side by shrubs. This is typical chaparral habitat, although the proximity of the creek provides moisture for other plants to grow. Among them is the California wild grape (Vitis californica), a vine that can be seen covering much of the vegetation on the right side of the trail. These plants produce their fruits in late summer, and are a very important food source for birds and other animals. Look past the wild grapes to the creek, where you can see young cottonwoods (Populus fremontii) and willows (Salix spp.) that rooted after the major storm-generated rock slides and floods of 1995.19. Spicebush. Several spicebush (Calycanthus occidentalis) plants grow here. True to their name, spicebush leaves are quite pungent. In the spring, these trees produce large deep red flowers with many petals. 20. Chaparral plants. This section of the trail is bordered by extensive chaparral. These plants are extremely well adapted to fire - new branches and foliage sprout from the old rootstocks. Chief among these plants is chamise, the wiry bush with tiny leaves that dominates this area. The area in which you are standing burned in 1988 and resprouted. It is very difficult to see now that it burned at all.21. Side trail. A scrub oak (Quercus berberidifolia) marks a fork in the path. The left fork is the main trail, and a side trail on the right will take you to toward the creek. In the spring, the flowing creek forms a pool here. This is a great place to look for aquatic insects, California Newts (Taricha torosa), and other animals. On a large boulder at the end of the trail is a rounded hole in the rock. This is a mortar made by the Patwin Native Americans who lived here until the 1800s. They used this mortar to grind acorns and into flour, which formed the staple of their diet.22. Cold Creek. Return to the main trail. The trail next crosses the bed of Cold Creek. In most years, this stream flows for about seven months (November-May). When it

starts flowing, it is quickly colonized by aquatic insects such as waterstriders (Gerris remigis), and stringy algae. In the summer, pools of water are left behind when the stream stops flowing and are important sources of water for wildlife. The creek crossing is also a good place to look at plants. The plants growing in and along the streamcourse are mulefat (Baccharis salicifolia), which looks like willow, but is a completely different species of plant. On the steep left side of the creek, blue larspur (Delphinium hesperium) makes a showy display in the spring. Just after the creek crossing, the vertical slope on the right yields a colorful display of red larkspur (Delphinium nudicaule) in early spring.23. Gray or Foothill pine tree. About 50m past the creek crossing, there is a large tree along the trail on your left - this is a gray or foothill pine (Pinus sabiniana).24. Bedrock underlying Cold Creek. As the trail continues upstream, look for a side trail on the left leading down to the creek. At this point in the canyon, the shale bedrock underlying the canyon makes its appearance. In the spring, the gray layers of the Yolo Formation form the bottom of the pools in this section of the creek. In the summer and fall, these pools have dried up, allowing you to inspect the bedrock. Shale is easily eroded by the action of water, so outcrops of the Yolo Formation are difficult to find in Cold Canyon.25. Cottonwood tree. As you cross the small bridge on the trail, you will have a good view of a cottonwood tree growing right in the stream channel. Cottonwoods are important riparian (“riverside”) trees, requiring water around the roots. This is a good spot to watch birds, such as Black Phoebes (Sayornis nigricans) and Bewick’s Wrens (Thyromanes bewickii).26. Scrub oak. The trail now climbs through chaparral, and this spot marks the location of a large scrub oak growing up and over you. The shade of the chapparal keeps this area relatively cool and moist, enabling maidenhair ferns (Adiantum jordanii) and mushrooms to thrive even after the spring rains have ceased.27. Tunnel of brush. The chaparral now has become a veritable tunnel of buckbrush (Ceanothus cuneatus). As you pass through, birds and small mammals can be heard skittering about just out of sight on either side of you.28. Wildhorse canyon. At this marker is a good view of the southern section of Cold Canyon Reserve. Cold Canyon continues south parallel to the trail, and joins with

Wildhorse Canyon to the left in the distance. This wild area is owned partly by the University and partly by the Bureau of Land Management.29. No entry fence. This fence was constructed to keep people from climbing this tempting open hillside. Even a small trail in this fragile land could start a major landslide.30. Homestead. A short distance further the trail crosses the Vlahos homestead. The open area around you was probably cleared by Vlahos and the soil compacted by livestock, mainly goats. One indication of this is star thistle (Centaurea solstitialis), a native of Asia that thrives on poor, overgrazed soils. The grassland is currently being treated to control this invasive pest, and to restore the native grassland vegetation that used to grow here.31. Homestead foundations. The stone wall on the left is about all that remains of the Vlahos’ former farmhouse. Walk around the foundations and you can find the former site of a well, some rusted metal, and a few rotted wood boards, but little else remains to remind us that this site was once a bustling household. Beyond the homestead, the trail continues into a shady glen. In the spring, look for the large white and purple blossoms of the iris (Iris macrosiphon) and the faded-red flowers of the Indian warrior (Pedicularis densiflora) on the right side of the trail. Cross the creek to the foundations of the old cold storage shed and the end of the Homestead Trail.32. Cold storage area. This area is delightfully cool and moist all summer long. The trees here include California bay and spicebush, but several large bigleaf maples (Acer macrophyllum) provide most of the shade. In the fall, the leaves of the maples turn color and bathe the glen in a wonderful orange light. In the spring, follow the creek up from the cold storage foundation to a small waterfall. Here Cold creek pours over some boulders into a small pool that often contains a variety of aquatic wildlife.

Enjoy the trip back down the trail! Or take the fork at the homestead foundation to The Blue Ridge Loop Trail.

Waterstrider

Flowering bigleaf maple

California Newt

California pipevine